Instructables

Design a Jet With The Unknown Basics!

Step 5: Burn!! Maw ha ha!!

Now that you have some compressors to choose from in your design, lets move on to FIRE. More specifically the combustion chamber which will create and direct your energy. The chamber is connected to rear of the compressor \ compressor outlet.

You'll need to design three primary systems:

*ignition
*fuel injector(s) \ nozzle(s)
*burner can

Ignition can be as simple as a lighter or an electric igniter. It's as simple or complex as you want it to be. best option is an electric igniter probably.

fuel injectors or nozzles are important as they atomize the fuel into a fine mist ideally for optimum combustion. A simple pulse jet has but one nozzle while aircraft engines can have 16 in a ring like formation. The nozzle should face away from the direction of air flow and is placed at the front of the chamber (the front being where the air comes in (unless a pulse jet). You'll also need to figure out how your fuel is going to be forced through the nozzle. You could have a pump or have a pressurized container like a propane tank (which is common for pulse jets).

Okay, now for the burner can. You might know this as a flame holder or some such. Without it, your combustion section would likely melt or deform under the intense heat. It's a can like structure that directs the flame onto your turbine. I should mention pulse jets don't need them (which is why they glow sizzling red hot). The fuel nozzle is aimed into the front of the burner can (front being what the air enters from). Your igniter will also need to enter the can to start combustion. The burner can has many small holes drilled along its entire surface. This allows air from your compressor to enter the inside of the burner can and focus the flame's path. The hot expanding gases from the burner can are then directed aft onto the turbine. For a better understanding, look closely at the configuration(s) in the pics. Oh and it will need to be made of a metal that can hold up under high temps.
 
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MistaMista2 years ago
Sorry, but in the second illustration, would there be a seal around the flame tube at the end of it so as to keep air from exiting unburned? Like would it be blocked off so that the only path for compressed air is to go through the holes in the flame tube and then get burned and exit through the end of the flame tube? Or should there be some opening for cooling reasons or something of that sort?
--= Excogitate =-- (author)  MistaMista2 years ago
In the engines I've seen some of the air is used for cooling the turbine and engine housing. This excess air is 'unburned' and goes around the combustion chamber. Though I have not seen a design with a seal, I have seen ones that get closer to turbine inlet. I can't see why it wouldn't be possible to design one with a seal.